This invention relates to an oil shock absorber system for motorcycles or automobiles and in particular for vehicles that are used either for racing or for all-terrain driving.
An oil shock absorber that comprises a mobile piston in a cylinder which, during its compression travel, displaces the oil that is contained in a chamber toward, on the one hand, a reservoir and, on the other, a second chamber that is located on the other side of the piston, is known from U.S. patent application Ser. No. 4,958,706. The path of the oil toward the second chamber that is located on the other side of the piston runs through valves for adjusting the resilience characteristics of the shock absorber. The pressure of the oil that is driven into the reservoir is balanced by a pocket that holds a pressurized gas and that plays, as it were, a role equivalent to that of the spring in the spring shock absorbers of the prior art. Access to the chamber of the reservoir is limited by, on the one hand, a system that can be adjusted by a screw for adjusting the compression rate, and, on the other, a valve for protection against excessive pressure that is set to withstand a maximum pressure of about 140 Kg/cm.sup.2 (2000 psi).
A shock absorber system that comprises a cylinder in which a mobile piston delimits two working volumes is also known from International Patent Application WO 94 12360. Each volume is connected, via a pipe, to an intermediate volume. The two intermediate volumes each communicate by three orifices with the same control chamber. The three orifices respectively comprise a valve for regulating the flow of oil from the intermediate volume to the control chamber, an adjustable nonreturn valve that constitutes a hydraulic brake, and a valve that allows a permanent passage from the control chamber to the intermediate volume. This relatively complex system makes it possible to adjust the characteristics of compression and of stress relief of a shock absorber independently, but it does not allow optimum adjustment of the shock absorber for operations in a range of displacement speeds of the piston that lies between low speeds and hydraulic brake speeds.
This invention relates to an oil reservoir that can be used with such a shock absorber or with other simpler or more complex shock absorber types. Actually, it has been noted that in these shock absorber systems, an elastic element that generally consists of a rubber ring is always provided on the shock absorber, between, on the one hand, ring (11) that is placed at the end of rod (10) of the piston that is adjacent to attachment ring (12) on the frame of the vehicle and, on the other hand, lower outside surface (151) of cylindrical body (15) that constitutes the compression chamber which forms the shock absorber stop that is encountered under extreme operating conditions. Actually, since the shock absorber is protected against excessive pressure, the valve of the reservoir is likely to open when the vehicle falls back after a major bounce, and, in this case, the only protection for the shock absorber is the elastic bearing that is located between cylinder (15) and ring (11).
The elastic bearing has the drawback of generating uncontrollable bouncing phenomena for the driver which sometimes bring the vehicle to tip violently to the front.